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Reanalysis and Observational Datasets and Variables Available on the WRIT Monthly Composite Mapping Page

Reanalyses and observational datasets available on the page are listed in the tables that follow. For more information and discussion of various atmospheric and oceanic reanalyses, see the "Reanalysis Intercomparison and Observations Wiki" (http://reanalyses.org). This wiki includes references/citations and a detailed reanalyses comparison table.
Different reanalysis datasets have different pressure levels output so you may need to consider that when differencing variables. Datasets are produced at differing spatial resolutions. Plot differences are computed by interpolating the lower resolution dataset of the two being compared to the resolution of the higher resolution and subtracting. Anomalies are based on the climatology from each reanalyses dataset separately. Variable units have been changed to be consistent so the datasets can easily be compared.

This reanalysis was the first of its kind for NOAA. NCEP used the same climate model that was initialized with a wide variety
of weather observations: ships, planes, RAOBS, station data, satellite observations and many more. By using the same model,
scientists can examine climate/weather statistics and dynamic processes without the complication that model changes can cause. The dataset is kept current using near real-time observations.

NCEP produced a second version of their first reanalysis starting from the beginning of the major satellite era. More observations were added, assimilation errors were corrected and a better version of the model was used.

The 20th Century Reanalysis version 2 dataset contains global
weather conditions and their uncertainty in six hour intervals from the
year 1871 to 2010. Surface and sea level pressure observations are
combined with a short-term forecast from an ensemble of integrations
of an NCEP numerical weather prediction model using the recently
developed Ensemble Kalman Filter technique to produce an estimate
of the complete state of the atmosphere, and the uncertainty in
that estimate. Additional observations and a newer version of the
NCEP model that includes time-varying CO2 concentrations, solar
variability, and volcanic aerosols are used in version 2. The long
time range of this dataset allows scientists to examine better long
time scale climate processes such as the Pacific Decadal Oscillation
and the Atlantic Multidecadal Oscillation as well as looking at the
dynamics of historical climate and weather events. Verification
tests have shown that using only pressure creates reasonable
atmospheric fields up to the tropopause. Additional tests suggest
some correspondence with observed variations in the lower stratosphere.

The National Centers for Environmental Prediction (NCEP) Climate Forecast System Reanalysis (CFSR) was completed over the 31-year period of 1979 to 2009 in January 2010. The CFSR was designed and executed as a global, high resolution, coupled atmosphere-ocean-land surface-sea ice system to provide the best estimate of the state of these coupled domains over this period. The current CFSR will be extended as an operational, real time product into the future.

NASA Modern Era Reanalysis for Research and Applications (MERRA): 1979-present (MERRA Home page)

MERRA is a NASA reanalysis for the satellite era using a major new version of the Goddard Earth Observing System Data Assimilation System Version 5 (GEOS-5) produced by the NASA GSFC Global Modeling and Assimilation Office (GMAO). The Project focuses on historical analyses of the hydrological cycle on a broad range of weather and climate time scales and places the NASA EOS suite of observations in a climate context.

ERA-Interim was originally planned as an 'interim' reanalysis in preparation for the next-generation extended reanalysis to replace ERA-40. It uses a December 2006 version of the ECMWF Integrated Forecast Model (IFS Cy31r2). It originally covered dates from 1 Jan 1989 but an additional decade, from 1 January 1979, was added later. ERA-Interim is being continued in real time. The spectral resolution is T255 (about 80 km) and there are 60 vertical levels, with the model top at 0.1 hPa (about 64 km). The data assimilation is based on a 12-hourly four-dimensional variational analysis (4D-Var) with adaptive estimation of biases in satellite radiance data (VarBC). With some exceptions, ERA-Interim uses input observations prepared for ERA-40 until 2002, and data from ECMWF's operational archive thereafter.
An pen-access journal article describing the ERA-Interim reanalysis is now available from the Quarterly Journal of the Royal Meteorological Society and should be used as the citation.

JMA carried out the second reanalysis project (known as the Japanese 55-year Reanalysis, or JRA-55) using a more sophisticated DA system based on the operational system as of December 2009, and newly prepared dataset of past observations. The analysis period covers the 55 years from 1958, when regular radiosonde observation began on a global basis. Many of the deficiencies of JRA-25 are alleviated in JRA-55 because the DA system used for the project featured a variety of improvements introduced after JRA-25. As a result, the JRA-55 project produced a high-quality homogeneous climate dataset covering the last half century.
References